U.S. patent number 4,809,572 [Application Number 07/128,925] was granted by the patent office on 1989-03-07 for power driven screwdriver.
This patent grant is currently assigned to Makita Electric Works, Ltd.. Invention is credited to Katsuhiko Sasaki.
United States Patent |
4,809,572 |
Sasaki |
March 7, 1989 |
Power driven screwdriver
Abstract
A power driven screwdriver includes a housing, a drive motor
mounted within the housing, and a main gear rotatably driven by the
drive motor. A spindle is axially movably supported within the
housing and has a driver bit secured thereto. The spindle has a
groove formed in the rear end thereof. A claw clutch mechanism is
provided and is actuated by axial movement of the spindle so as to
transmit and disconnect the rotation of the main gear to the
spindle. The claw clutch mechanism includes a fixed clutch member
formed on the main gear and a movable clutch member mounted on the
spindle adjacent the rear end thereof. The movable clutch member
has a groove formed in the forward end thereof in opposed relation
to the groove of the spindle. One of the grooves of the spindle and
the movable clutch member is configured to form an axially inclined
groove. Engaging means is interposed between the groove of the
spindle and the groove of the movable clutch member. A spring is
positioned between the main gear and the movable clutch member and
is adapted to normally urge the movable clutch member in a
direction away from the fixed clutch member.
Inventors: |
Sasaki; Katsuhiko (Anjo,
JP) |
Assignee: |
Makita Electric Works, Ltd.
(Anjo, JP)
|
Family
ID: |
17786970 |
Appl.
No.: |
07/128,925 |
Filed: |
December 4, 1987 |
Foreign Application Priority Data
|
|
|
|
|
Dec 9, 1986 [JP] |
|
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61-292835 |
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Current U.S.
Class: |
81/429;
81/58.3 |
Current CPC
Class: |
B25B
21/00 (20130101); B25B 23/0064 (20130101) |
Current International
Class: |
B25B
23/00 (20060101); B25B 21/00 (20060101); B25B
023/00 () |
Field of
Search: |
;81/58.3,57,57.11,57.12,57.13,57.14,429,451 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Schmidt; Frederick R.
Assistant Examiner: Rachuba; Maurina
Attorney, Agent or Firm: Dennison, Meserole, Pollack &
Scheiner
Claims
What is claimed is:
1. A power driven screwdriver for driving a screw into a work,
comprising:
a housing having a forward and a rear end;
a drive motor mounted within said housing;
a fixed clutch member also mounted within said housing and driven
by said drive motor;
a spindle rotatably supported within said housing and disposed
forwardly of said fixed clutch member, said spindle being axially
movable for a predetermined distance;
a stopper sleeve attached to the forward end of said housing;
a driver bit mounted to the forward end of said spindle, said
driver bit being inserted into said stopper sleeve such that when
the forward end of said stopper sleeve abuts on the work, said
driver bit is restrained from moving further toward the work;
a movable clutch member mounted within said housing in opposed
relation to said fixed clutch member and engageable with said fixed
clutch member;
engaging means for engaging said movable clutch member with said
spindle such that said movable clutch member moves a predetermined
distance with respect to said spindle in both axial and
circumferential directions of said spindle, the axial and
circumferential movements of said movable clutch member being
correlated such that when said movable clutch member is rotated by
said drive motor in one circumferential direction with respect to
said spindle, said spindle moves forwardly with respect to said
movable clutch member and when said movable clutch member is
rotated in the other circumferential direction with respect to said
spindle, said movable clutch member moves axially with respect to
said spindle in a direction away from said fixed clutch member;
and
a spring adapted to normally urge said movable clutch member in a
direction away from said fixed clutch member;
whereby when said driver bit is pushed onto the screw, said spindle
is moved rearwardly to thereby move said movable clutch member
rearwardly until the latter engages said fixed clutch member;
and
whereby when the screw is driven into the work to a predetermined
depth, the forward end of said stopper sleeve abuts on the work and
said movable clutch member is disengaged from said fixed clutch
member, and by reason of the absence of torque between said movable
clutch member and said spindle and by reason of the biasing action
of said spring, said movable clutch member is moved away from said
fixed clutch member until said movable clutch member and said fixed
clutch member are brought to their fully non-contacting
position.
2. The power driven screwdriver as defined in claim 1 wherein said
spindle is formed with a first groove on a surface thereof opposite
to said movable clutch member, said movable clutch member is formed
with a second groove on a surface thereof in generally opposed
relation to said first groove, and an engaging member is interposed
between said first and second grooves, and wherein at least one of
said first and second grooves extends a predetermined distance in
the circumferential direction of said spindle and is configured to
smoothly vary the axial position thereof as the circumferential
position thereof varies, and the other groove is sized to receive
at least a portion of said engaging member therein.
3. The power driven screwdriver as defined in claim 2 wherein said
at least one of said first and second grooves is of configuration
corresponding substantially to a part of spiral.
4. The power driven screwdriver as defined in claim 2 wherein said
other groove extends in a direction axially of said spindle.
5. The power driven screwdriver as defined in claim 2 wherein said
first groove is spiral and is formed on an outer periphery of the
rear end of said spindle.
6. The power driven screwdriver as defined in claim 2 wherein said
spindle is formed with three first grooves spaced substantially
equally apart on an outer periphery of said spindle, and wherein
said movable clutch member is engaged with said spindle in
substantially concentric relation.
7. The power driven screwdriver as defined in claim 2 wherein said
engaging member is a ball.
8. The power driven screwdriver as defined in claim 1 wherein said
spindle is formed with a first recess on a surface thereof opposite
to said movable clutch member, said first recess having a
predetermined width and length extending from the rear end to the
forward end of said spindle, said movable clutch member is formed
with a second recess formed on a surface thereof opposite to said
spindle, said second recess having a predetermined width and length
extending from the forward end to the rear end of said movable
clutch member, and an engaging member is interposed between said
first and second recesses, and wherein at least one of said first
and second recesses is configured to smoothly vary the length
thereof as the transverse position thereof varies, and the other
recess is sized to receive at least a portion of said engaging
member therein.
9. The power driven screwdriver as defined in claim 8 wherein said
first recess is formed on an inner periphery of said spindle, and
wherein said second recess is formed on an outer periphery of said
movable clutch member.
10. The power driven screwdriver as defined in claim 8 wherein said
spindle is formed with three first recess spaced substantially
equally apart on an inner periphery thereof, and wherein said
movable clutch member is engaged with said spindle in substantially
concentric relation.
11. The power driven screwdriver as defined in claim 8 wherein said
engaging member is a ball.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power driven screwdriver, and
more particularly to a clutch mechanism for such a screwdriver
which will transmit rotation from a drive motor to a spindle with a
driver bit.
2. Description of the Prior Art
Such power driven screwdrivers may include a drive motor, a main
gear rotated by the drive motor, an axially movable spindle having
a driver bit secured thereto, and clutch means adapted to transmit
and disconnect the rotation from the drive motor to the spindle.
Basically, the clutch means includes a claw clutch mechanism which
is composed of a fixed clutch member formed on the main gear and a
movable clutch member mounted on the spindle and adapted to engage
the fixed clutch member. Thus, axial movement of the spindle causes
the movable clutch member to move into and out of driving
engagement with the fixed clutch member. Such screwdrivers are
disclosed, for example, in U.S. Pat. Nos. 2,940,488, 3,527,273 and
3,712,352.
In such screwdrivers using a simple claw clutch mechanism, however,
the rotation of the spindle is restrained at the completion of a
screw driving operation, thereby causing the clutch mechanism to
temporarily repeat its engaging and disengaging operation. This
will generate clanging sounds, giving unpleasant feeling to the
operator, and cause early wear of the clutch mechanism.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a
power driven screwdriver having a clutch mechanism which may be
smoothly disengaged at the completion of a screw driving operation
so as to avoid unpleasant clanging sounds.
It is another object of the present invention to provide a power
driven screwdriver which will improve efficiency of driving
operation and enhance long life of the clutch mechanism.
The power driven screwdriver includes, according to the present
invention, a housing, a drive motor mounted within the housing, and
a main gear rotatably driven by the drive motor. A stopper sleeve
is attached to the forward end of the housing. A spindle is axially
movably supported within the housing and has a driver bit disposed
within the stopper sleeve. The spindle has a groove formed in the
rear end thereof. A claw clutch mechanism is provided and is
actuated by axial movement of the spindle so as to transmit and
disconnect the rotation of the main gear to the spindle. The claw
clutch mechanism includes a fixed clutch member formed on the main
gear and a movable clutch member mounted on the rear end of the
spindle so as to engage the fixed clutch member. The movable clutch
member has a groove formed in the forward end thereof in opposed
relation to the groove of the spindle. At least one of the grooves
of the spindle and the movable clutch member is configured to form
an axially inclined groove. Engaging means is interposed between
the groove of the spindle and the groove of the movable clutch
member. A spring is positioned between the main gear and the
movable clutch member and is adapted to normally urge the movable
clutch member in a direction away from the fixed clutch member.
Thus, when the driver bit held by the spindle is pressed against a
work surface, the spindle is pushed rearwardly in the axial
direction and thence the engaging means is moved in the inclined
groove of the spindle or the movable clutch member. As this occurs,
the movable clutch member is moved toward the fixed clutch member
against the biasing force of the spring, until the movable clutch
member engages the fixed clutch member. Rotation from the drive
motor is then transmitted to the spindle. When the stopper sleeve
attached to the housing engages the work surface, the spindle and
the movable clutch member are pushed forwardly by the amount
corresponding to the height of teeth of the fixed clutch member, so
that the movable clutch member is disengaged from the fixed clutch
member, terminating the transmission of rotation. Simultaneously
therewith, the biasing force of the spring causes the movable
clutch member to be completely disengaged from the fixed clutch
member through the shifting movement of the engaging means along
the inclined groove.
The present invention will become more fully apparent from the
claim and the description as it proceeds in connection with the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view, partially in section, of a power driven
screwdriver according to a first embodiment of the present
invention;
FIG. 2 is an exploded perspective view of the essential parts of
the screwdriver;
FIG. 3 is an enlarged side sectional view of the essential parts of
the screwdriver in its operating position;
FIG. 4 is an enlarged sectional view taken along the line IV--IV of
FIG. 3;
FIG. 5 is a side view of the clutch mechanism in its disengaged
position;
FIG. 6 is a side view of the clutch mechanism in its engaged
position;
FIGS. 7A to 7F are schematic views illustrating various phases of
operation through the screwdriver;
FIG. 8 is a side view, partially in section, of a power driven
screwdriver according to a second embodiment of the present
invention;
FIG. 9 is an enlarged sectional view taken along the line IX--IX of
FIG. 8; and
FIG. 10 is a schematic view showing the engaging grooves in
developed form.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIGS. 1 to 4, shown therein is a power driven
screwdriver according to a first embodiment of the present
invention. As shown therein, the screwdriver includes a housing 1
having a cylindrical portion 1a. The housing 1 contains a drive
motor (not shown) having a shaft on which a gear 2 is formed. The
gear 2 drivingly engages a main gear 3 fixed to a support shaft 4.
A spindle 5 is rotatably and axially movably supported within the
cylindrical portion 1a of the housing 1 in coaxial relation to the
support shaft 4. The forward end of the spindle 5 has a driver bit
6 secured thereto, and the rear end of the spindle 5 is located in
spaced apart opposed relation to the main gear 3.
A claw clutch mechanism 7 is provided between the main gear 3 and
the spindle 5 and is comprised of a fixed clutch member 8 and a
movable clutch member 9. The fixed clutch member 8 is formed on the
forward surface of the main gear 3. The movable clutch member 9 is
of generally ring-shaped configuration and is fitted coaxially on
the spindle 5 adjacent the rear end thereof so as to engage the
fixed clutch member 8.
As shown in FIGS. 2 and 4, the spindle 5 has, in the outer
periphery of the rear end thereof, three grooves 10 formed at equal
intervals and inclined a predetermined extent in the axial
direction. The movable clutch member 9 has, in the inner periphery
thereof, three engaging grooves 11 each formed in opposed relation
to each inclined groove 10 of the spindle 5 and having a forwardly
opening end. An engaging ball 12 is received between each pair of
opposite grooves 10 and 11.
Thus, the movable clutch member 9 is moved between positions in
which it is respectively engaged with and disengaged from the fixed
clutch member 8 through axial movement of the spindle 5 and through
axial movement of the engaging balls 12 received between the
inclined grooves 10 and the engaging grooves 11.
A spring 13 is provided between the main gear 3 and the movable
clutch member 9 and is adapted to normally urge the movable clutch
member 9 in a direction away from the fixed clutch member 8.
A cylindrical stopper sleeve 14 is threadably secured to the front
end of the cylindrical portion 1a of the housing 1, retaining the
driver bit 6 with its tip projected therefrom. The amount of
projection of the tip of the driver bit 6 may be adjusted by
changing the axial position of the stopper sleeve 14 relative to
the depth to which a screw Y may be driven into a work W.
The operation of the first embodiment thus constructed will now be
described with reference to FIGS. 5, 6 and 7A to 7F.
Assuming that the desired predetermined depth adjustment has been
made, the tip of the driver bit 6 is applied to the head of the
screw Y to be driven, and the screw Y is positioned on the work
W.
In this position, the engaging balls 12 in the inclined grooves 10
and the engaging grooves 11 are located remote from the main gear
3, or in the lowermost position as viewed in FIG. 5. The movable
clutch member 9 is in disengaged position and therefore, when the
drive motor is rotated, only the main gear 3 is rotated; rotation
of the drive motor is not transmitted to the spindle 5 and the
driver bit 6 (FIG. 7A).
As the operator exerts pressure on the screw Y by pushing forwardly
on the tool, the spindle 5 will move rearwardly toward the main
gear 3 and thence, the movable clutch member 9 will move against
the biasing force of the spring 13 until it engages the fixed
clutch member 8. Thereupon, the rotation from the drive motor will
be transmitted to the spindle 5 through the main gear 3, causing
the driver bit 6 to rotate (FIG. 7B).
As the screw Y is being driven by the driver bit 6, the movable
clutch member 9 will completely engage the fixed clutch member 8.
The engaging balls 12 in the inclined grooves 10 and the engaging
grooves 11 will be moved to the uppermost position as viewed in
FIG. 6. As the result, the spindle 5 will be pushed to the extent
of the axial inclination amount a of the inclined grooves 10,
providing a clearance a' between the fixed clutch member 8 and the
movable clutch member 9 (FIG. 7C).
As the screw Y is further driven into the work W, the entire tool
will be advanced relative to the work W until such time when the
end of the stopper sleeve 14 has engaged the work surface.
Thereupon, the spindle 5 and the movable clutch member 9 is pushed
forwardly by the amount corresponding to the height b of the teeth
of the fixed clutch member 8, causing the driver bit 6 to drive the
screw Y to that extent b. The movable clutch member 9 will then be
disengaged from the fixed clutch member 8 (FIGS. 7D and 7E).
As soon as the movable clutch member 9 is disengaged from the fixed
clutch member 8, the engaging balls 12 will moved under the action
of the spring 13 along the inclined grooves 10 in a direction away
from the main gear 3; and the movable clutch member 9 will be moved
by the clearnace a' corresponding to the inclination amount a of
the inclined grooves 10, thus providing that clearance a' between
the fixed clutch member 8 and the movable clutch member 9.Here, the
movable clutch member 9 is completely disengaged from the fixed
clutch member 8, disconnecting the rotation from the main gear 3 to
the spindle 5 (FIGS. 7E and 7F).
Thus, it can be seen that the disengagement between the fixed
clutch member 8 and the movable clutch member 9 may be effected
both smoothly and reliably without producing clanging sounds.
Referring to FIGS. 8 to 10, shown therein is a second embodiment of
the present invention. As in the first embodiment, a power driven
screwdriver includes a housing 15 having a cylindrical portion 15a.
The housing 15 contains a drive motor (not shown) having a shaft on
which a gear 16 is formed. The gear 16 drivingly engages a main
gear 17 fixed to a support shaft 18. A spindle 19 is rotatably and
axially movably supported within the cylindrical portion 15a of the
housing 15 in coaxial relation to the support shaft 18. The forward
end of the spindle 19 has a socket bit 20 secured thereto, and the
rear end of the spindle 19 is located in spaced apart opposed
relation to the main gear 17.
A claw clutch mechanism 21 is provided between the main gear 17 and
the spindle 19 and is comprised of a fixed clutch member 22 and a
movable clutch member 23. The fixed clutch member 22 is formed on
the forward surface of the main gear 17. The movable clutch member
22 is fitted coaxially in the rear end of the spindle 19 so as to
engage the fixed clutch member 23.
The rear end of the spindle 19 has a flange 24 formed integrally
therewith. The flange 24 has a circular recess 25 formed in the
rear end thereof. As shown in FIG. 9, three, peripherally
extending, engaging grooves 26 are cut at equal intervals from the
rear end of the flange 24 to the bottom of the recess 25. Each of
the engging grooves 26 has, on the bottom thereof, a substantially
V-shaped sloping surface 26a tapared in a direction axially of the
spindle 19, as shown in FIG. 10.
The movable clutch member 23 has a boss 23a L and a flange 23b
formed integrally therewith. The boss 23a is loosely fitted in the
recess 25 of the flange 24 of the spindle 19. As shown in FIGS. 9
and 10, the boss 23a has, in the outer periphery thereof, three
engaging grooves 27 each formed in opposed relation to each
engaging groove 26 of the flange 24. As with the engaging grooves
26 of the flange 24, each of the engaging grooves 27 of the boss
23a has, on the bottom thereof, a substantially V-shaped sloping
face 27a tapered in a direction axially of the spindle 19 and
symmetric with the sloping surface 26a of the flange 24. An
engaging ball 28 is received between each pair of opposite grooves
26 and 27.
Thus, the movable clutch member 23 is moved between positions in
which it is respectively engaged with and disengaged from the fixed
clutch member 22 through axial movement of the spindle 19 and
through axial movement of the engaging balls 28 received between
the engaging grooves 26 having axially sloping surfaces 26a and the
engaging grooves 27 having axially sloping surfaces 27a.
A spring 29 is provided between the main gear 17 and the movable
clutch member 23 and is adapted to normally urge the movable clutch
member 23 in a direction away from the fixed clutch member 22.
A cylindrical stopper sleeve 30 is threadably secured to the front
end of the cylindrical portion 15a of the housing 15, retaining the
socket bit 20 with its tip projectted therefrom. The amount of
projection of the tip of the socket bit 20 may be adjusted by
changing the axial postion of the stopper sleeve 30 relative to the
depth to which a screw may be driven into a work.
The operation of the second embodiment is substantially the same as
that of the first embodiment, except that the movement of the
engaging balls 28 is controlled in the axially sloping surface 26a
and 27a of the engaging grooves 26 and 27, respectively. Thus, the
same effect as that of the first embodiment may be attained in the
second embodiment.
Although the inclined grooves 10 of the first embodiment are formed
on the spindle 5, they may be formed on the movable clutch member
9.
The clutch mechanism of the present invention may be readily
adapted to pneumatic screwdrivers. Further, as will be apparent to
those skilled in the art, various changes and modifications may be
made without departing from the spirit of the present invention
which is defined by the appended claims.
* * * * *